1. Field of the Disclosure
This disclosure relates to a semiconductor light emission device, and more particularly to a semiconductor light emission device adapted to improve reliability through a uniform current flow.
2. Description of the Related Art
In general, light emission diodes (LEDs) have a basic structure which includes n-type semiconductor layer, a light emission layer, and a p-type semiconductor layer sequentially epitaxied on a crystal substrate. The light emission layer can be formed in one of double hetero (DH), single quantum well (SQW), and multi quantum well (MQW) structures. Any one of a Sic substrate, a GaN substrate, a sapphire substrate, and others can be used as a crystal substrate. The n-type semiconductor layer, the crystal substrate, and the p-type semiconductor layer are formed to include outlet electrodes, respectively.
FIG. 1 is a cross-sectional view schematically showing the structure of a semiconductor light emission device according to the related art. Referring to FIG. 1, the semiconductor light emission device structurally includes a sapphire substrate 1 suitable to transmit light, a buffer layer 10 formed on the sapphire substrate 1, and a sequentially stacked layer of an n-type clad layer 20, an active layer 30 and a p-type clad layer 40 which is formed on the buffer layer 10.
The active layer has a MQW structure containing InGaN. The n-type clad layer 20, the active layer 30, and the p-type clad layer 40 are sequentially formed by performing an epitaxial growth process. The p-type clad layer 40 and the active layer 30 is partially removed from the n-type clad layer 20 by performing a mesa etching process, so as to expose a part of the upper surface of the n-type clad layer 20.
The light emission device further includes an n-type electrode formed on the partially exposed upper surface of the n-type clad layer 20, and a transparent conductor layer 50 and a p-type electrode 60 sequentially stacked on the p-type clad layer 40. The transparent conductor layer 50 is formed from indium-tin-oxide (ITO) or others.
In this manner, the semiconductor light emission device uses the sapphire substrate 1 with the light transmitting property as a nonconductor substrate. The p-type and n-type electrodes 60 and 70 are formed on upper surfaces of the epitaxially grown layers, respectively, while the semiconductor light emission device with the sapphire substrate 1 is manufactured.
Such a semiconductor light emission device causes a current flowing between the p-type and n-type electrodes 60 and 70 to be excessively concentrated to the etched surfaces of the p-type clad layer 40 and the active layer 30. This regionally excessive concentration phenomenon of the current flow deteriorates the reliability of the semiconductor light emission device using the sapphire substrate 1.